JP3397001B2 - Encoding method and apparatus, decoding apparatus, and recording medium - Google Patents

Abstract

PURPOSE: To realize a high degree compression of a multi-channel signal by processing a digital signal of a part of channel as a common signal and applying coding processing to the signal. CONSTITUTION: Audio data of each channel of a center C, a left L, a right R, a left surround SL and a right surround SR from input terminals 101a-101e are given to a common processing analyzer 102. An output of the analyzer 102 is given to extracted devices 103a-103e of corresponding channels and a common component is extracted from the original audio data for each channel and only the remaining components are fed to coders 105a-105e. An output of the analyzer 102 is fed also to a common data generator 104, in which common data of each channel are collected and rearranged and then the result is outputted. Each coder 105 gives common processing parameter information to a multiplexer 106 together with the coding data and the data are multiplexed into one-bit-stream.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention, for example, compresses and encodes multi-channel signals used in stereo such as video disc players, video tape recorders, motion picture film movie systems, and so-called multi-surround audio systems. The present invention relates to an encoding method and device, a decoding device, and a recording medium.

[0002]

2. Description of the Related Art Conventionally, there are various techniques for high-efficiency coding of a signal such as audio or voice. For example, a signal on the time axis is divided into blocks in a predetermined time unit and the signal on the time axis for each block is There is so-called transform coding, which is a blocking frequency band division method in which a signal on the frequency axis is orthogonally transformed (spectral transform) to be divided into a plurality of frequency bands and each band is encoded.

Further, so-called band division coding (sub-band coding: a non-blocking frequency band division method) in which an audio signal on the time axis is not divided into blocks and is divided into a plurality of frequency bands for encoding. SBC) etc. can be mentioned. Further, a method of high efficiency coding in which the above band division coding and transform coding are combined is also considered, and in this case, for example, after performing band division by the band division coding, A signal for each band is spectrally converted into a signal on the frequency axis, and the spectrum-converted signal is encoded for each band.

Here, as the band division filter used in the above band division encoding, for example, QMF is used.
(Quadrature Miller Filter) and other filters, and this QMF filter is based on the document "Digital Coding of Speech in Subvans"("Digital co
ding of speech in subbands "RECrochiere, BellSy
st.Tech. J., Vol.55, No.8 1976).
This QMF filter divides the band into two equal bandwidths, and is characterized in that so-called aliasing does not occur when the divided bands are combined later. In addition, the document "Polyphase Quadrature filters -A new subb"
andcoding technique ", Joseph H. Rothweiler ICASSP
83, BOSTON) describes a method of equal bandwidth filtering. This polyphase quadrature filter is characterized in that when a signal is divided into a plurality of bands of equal bandwidth, it can be divided at one time.

Further, as the spectrum conversion of the above-mentioned orthogonal conversion, for example, the input audio signal is divided into blocks in a predetermined unit time (frame), and the discrete Fourier transform (DFT) and the discrete cosine transform (DC) are performed for each block.
T), modified discrete cosine transform (MDCT), etc. are used to convert a signal on the time axis into a signal on the frequency axis. The above MDCT
For the paper "Subband / Transform Coding Using Fil".
ter Bank Designs Based on Time Domain Aliasing Can
cellation, "JPPrincen ABBradley, Univ. of Surr
ey Royal Melbourne Inst. of Tech. ICASSP 1987).

In this way, by quantizing the signal divided for each band by the filter and the spectrum conversion,
It is possible to control the band in which the quantization noise is generated, and it is possible to perform auditory and more efficient encoding by utilizing the properties such as the so-called masking effect. In addition, if the normalization is performed for each band, for example, with the maximum absolute value of the signal component in that band before performing the quantization here,
Furthermore, highly efficient encoding can be performed.

Here, as the frequency division width in the case of quantizing each frequency component divided into frequency bands, for example, a bandwidth considering human auditory characteristics is often used. That is, the audio signal may be divided into a plurality of bands (for example, 25 bands) with a bandwidth generally called a critical band in which the higher the band, the wider the bandwidth. Further, when quantizing the data for each band at this time, a predetermined bit allocation for each band, or
Quantization is performed by adaptive bit allocation (bit allocation) for each band. For example, when the coefficient data obtained by the MDCT processing is quantized by the bit allocation, the MD of each block is
The MDCT coefficient data for each band obtained by the CT process is quantized by the adaptive allocation bit number (adaptive allocation bit number).

The following two methods are known as the above-mentioned bit allocation method (bit allocation method).

For example, the document "Adaptive Transform Coding of Speech Signal"
s ", IEEE Transactions of Accoustics, Speech, and S
ignalProcessing, vol.ASSP-25, No.4, August 1977)
In, bit allocation is performed based on the signal size of each band.

In addition, for example, the document "Critical Band Encoder-Digital Encoding of Perceptual Requirements of the Auditory System"("The critical band coder --digital encodin").
g of the perceptual requirements of the auditory s
ystem ", MAKransner MIT, ICASSP 1980) describes a method for obtaining a required signal-to-noise ratio for each band and performing fixed bit allocation by using auditory masking.

[0011]

By the way, for example, in the high-efficiency compression encoding system for audio signals using the above-mentioned sub-band coding or the like, the human auditory characteristic is utilized to convert the audio data into about 1 A method of compressing to / 5 has already been put into practical use. As a high-efficiency encoding method for compressing this audio data to about 1/5, for example, when recording audio data on a so-called mini disk (MD, trademark) which is a magneto-optical disk having a diameter of 64 mm. ATRAC (Adaptive TRa), which is the compression encoding method for audio data
There is a method called nsform Acoustic Coding (trademark).

Further, not only in the case of ordinary audio equipment but also in stereo or multi-surround sound systems such as motion picture film movie systems, high-definition televisions, video tape recorders, video disc players, etc., for example, 4 to 8 channels, etc. Are handling audio or voice signals of multiple channels of
Even in this case, it is desired to perform high efficiency coding that reduces the bit rate.

Particularly, for example, eight channels of digital audio signals of a left channel, a left center channel, a center channel, a right center channel, a right channel, a left surround channel, a right surround channel, and a subwoofer channel are recorded on the above-mentioned motion picture film. In such a case, high-efficiency coding that reduces the bit rate is required. That is, an area in which the above 8 channels of 16-bit linearly quantized audio data can be recorded at a sampling frequency of 44.1 kHz as used in so-called CD (Compact Disc, trademark), etc. It is difficult to secure the audio data, and it is therefore necessary to compress the audio data.

The above-mentioned 8 recorded on the above-mentioned motion picture film
Each channel is, for example, a left speaker, a left center speaker, a center speaker, a right center speaker, a right speaker, a surround arranged on the screen side where an image reproduced from the image recording area of the movie film is projected by the movie machine. It corresponds to a left speaker, a surround right speaker, and a subwoofer speaker, respectively. Here, the center speaker is arranged in the center of the screen side and outputs a reproduced sound based on the audio data of the center channel, and outputs the most important reproduced sound such as an actor's dialogue. The subwoofer speaker outputs a reproduced sound based on audio data of the subwoofer channel and effectively outputs a sound felt as vibration rather than a low frequency sound such as an explosion sound. It is often used effectively for such purposes. The left speaker and the right speaker are arranged on the left and right of the screen, and output a reproduced sound by the left channel audio data and a reproduced sound by the right channel audio data, and exhibit a stereo sound effect.
The left center speaker is arranged between the left speaker and the center speaker, and the right center speaker is arranged between the center speaker and the right speaker. The left center speaker outputs a reproduced sound based on the audio data of the left center channel, and the right center speaker outputs a reproduced sound based on the audio data of the right center channel. Each of the left center speaker and the right speaker plays an auxiliary role. Fulfill. Especially in a movie theater with a large screen and a large number of seats, the localization of the sound image tends to be unstable depending on the position of the seat, but by adding the above left center speaker and right center speaker, a more realistic localization of the sound image is created. Exert an effect on.

Further, the surround left speaker and the surround right speaker are arranged so as to surround a spectator's seat, and output a reproduced sound of left surround channel audio data and a reproduced sound of right surround channel audio data. It has the effect of giving an impression of sound, applause, and cheers. As a result, a more stereoscopic sound image can be created.

Further, since the surface of the medium called film is apt to be scratched, if the original digital data is recorded, the data will be seriously lost and it will not be put to practical use. For this reason, the capability of the error correction code becomes very important, and the data compression must be performed to the extent that it can be recorded in the recording area on the film including the correction code.

From the above, as a compression method for compressing the 8-channel digital audio data, the optimum bit allocation is performed in consideration of the characteristics of the human auditory sense as described above, so that, for example, in a CD or the like. The 16-bit digital audio data having a sampling frequency of 44.1 kHz to be recorded is compressed to about ⅕, and the high-efficiency encoding method (so-called ATRAC method or the like) that achieves sound quality comparable to that of the CD is applied. I am trying to do it.

However, the high-efficiency coding method for compressing the digital audio data to about 1/5 is a single-channel coding method, and when using this to code multi-channel audio data, It is not possible to perform effective data coding processing using factors such as data dependency between channels, data characteristics of each channel, and format characteristics.

In human hearing, the sense of direction tends to be uncertain with respect to sounds in the high frequency band. Therefore, in the high frequency band, data is shared between channels and coded, and this shared code is used. There is also a method of reducing the recording area by recording the converted data. However, although the sense of direction of the sound is uncertain, the level difference of the sound can be sensed, and thus when the sound is reproduced in multiple channels, it is perceived by the human ear as a change in the sound field, especially when the correlation between the channels is weak. It is often done.

In view of the above, the present invention can realize higher compression in the compression coding of multi-channel signals regardless of the degree of correlation of digital data between the multi-channels, and An object of the present invention is to provide an encoding method and device, a decoding device, and a recording medium that can be realized by using an existing encoder and decoder.

[0021]

The present invention has been made in view of such circumstances, and the encoding method of the present invention is
A coding method for coding a digital signal of a plurality of channels and outputting the coded digital signal and parameter information of the coding, wherein a digital signal of at least a part of the digital signals of the plurality of channels is shared. Commonizing step to make the signal into a unified signal, a changing step to change the combination of the channels to be made common according to the frequency characteristics of the digital signal or the intended reproduction environment, and a parameter indicating the combination of the made common channels. A parameter information output step of outputting information, an encoding step of encoding and outputting the common signal, and a multiplexing step of multiplexing the parameter information and the encoded output, thereby making it possible to solve the above problems. To solve.

The encoding device of the present invention is an encoding device that encodes digital signals of a plurality of channels and outputs the parameter information of the encoding together with the encoded digital signals. And a changing means for changing the combination of the channels to be shared according to the frequency characteristics of the digital signal and the intended reproduction environment. , Parameter information output means for outputting parameter information indicating a combination of the common channels, encoding means for encoding the common signals, and multiplexing for multiplexing the parameter information and the encoded output Means to solve the above problems.

Further, the decoding apparatus of the present invention handles a part or all of the digital signals of a plurality of channels as one or a plurality of common signals, and depending on the frequency characteristics of the digital signals and the intended reproduction environment. A decoding device for decoding encoded digital signals of a plurality of channels including a signal in which a combination of channels to be shared is changed using the parameter information of the encoding, and Decoding means for decoding the received signal,
Distribution means for distributing the decoded common signal to a plurality of channels in accordance with the combination of the commonization, and restoration means for restoring each digital signal of the plurality of channels based on the distributed commonized signal. It is characterized by having and.

Further, the recording medium of the present invention treats at least one channel signal of digital signals of a plurality of channels as a common signal, and the common signal according to the frequency characteristics of the digital signal and the intended reproduction environment. A signal obtained by changing the combination of channels to be standardized and encoding the common signal, parameter information indicating a combination of channels to be common, and a signal encoding another signal other than the common signal. And are recorded together with encoding parameter information.

[0025]

According to the encoding method and apparatus of the present invention, the compression rate is increased by treating the digital signals of at least some of the digital signals of a plurality of channels as common signals and performing the encoding process. Further, by changing the combination of channels to be shared according to the intended reproduction environment of the digital signal, or by changing the processing method handled as a common signal according to the recommended reproduction environment of the digital signal, for example, the digital signal is changed. When it is an audio signal, the change in the sound field due to commonization is suppressed.

Further, according to the encoding method and apparatus of the present invention, the combination of channels shared between predetermined time frames (eg, sound frames) and the instability caused by a sudden change in the processing method handled as common data are unstable. It is possible to avoid becoming a reproduction sound field.

Further, according to the decoding device of the present invention, digital signals of a plurality of channels are decoded from at least one common signal, and the common signal is generated according to the reproduction environment recommended by the coded signal. By changing the processing method to be handled, for example, when the digital signal is an audio signal, the change in the sound field due to the commonization is suppressed.

Further, according to the recording medium of the present invention, a signal encoded by the encoding method and apparatus of the present invention is recorded. By using an optical disc or a motion picture film, a more stable reproduction sound is produced. It becomes possible to provide a place.

[0029]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of an encoding device to which the encoding method of the present invention is applied. That is, the encoding apparatus of the present embodiment is an encoding apparatus that realizes multi-channel compression encoding by using a plurality of single-channel compression encoders (for example, the above-mentioned ATRAC encoder).

That is, the coding apparatus of the embodiment of the present invention is a coding apparatus which codes digital audio signals of a plurality of channels and outputs the parameter information of the coding together with the coded digital audio signals. Handling a part or all of the digital audio signal of 1 as one or a plurality of common signals, and changing the combination of channels to be common according to the frequency characteristics of the digital audio signal and the target reproduction environment, A common analyzer 102, a common data generator 1 are provided as coding means for coding the common signals.
04, encoders 105f to 105g.

Further, in FIG. 2, for comparison with the coding apparatus of the embodiment of the present invention, a multi-channel coding apparatus which performs compression coding for each channel (multi-channel when the present invention is not used An encoding device) is shown. For easy understanding, the same reference numerals are given to corresponding portions in FIGS. 1 and 2, and description thereof is omitted.

In this embodiment shown in FIG. 1, five-channel audio data of a center (C) channel, a left (L) channel, a right (R) channel, a left surround (SL) channel, and a right surround (SR) channel are output. It demonstrates using. In addition, subwoofer (ultra-low range)
5.1 channels can be configured by adding the channels of.

First, prior to the description of FIG. 1, in the configuration of FIG. 2, a center (C) channel, a left (L) channel, a right (R) channel, and a left surround, which are supplied via the input terminals 101a to 101e. The audio data of each of the (SL) channel and the write surround (SR) channel is a single-channel encoder 105a.
~ 105e. These encoders 105a to 105
In e, encoding is performed as described later, and the encoded data is sent to the multiplexer 106. The multiplexer 106 converts the encoded data of each channel into one bit stream, and the bit stream is output from the output terminal 107.

On the other hand, as shown in FIG. 1, the coding apparatus of the embodiment of the present invention supplies the center (C), the left (L), and the right (R) supplied through the input terminals 101a to 101e. , Left surround (SL) and right surround (SR) channels of audio data are first input to the common analyzer 102. Here, an effective common method and a range to be common to each channel, which will be described later, are selected, and only a common portion is selected and output from audio data of each channel. If they are not shared, nothing is output.

The output of the common analyzer 102 is the common data extractors 103a to 103a of the corresponding channels.
03e is input. Here, a common part is extracted from the original audio data for each channel, and only the remaining part is sent to the encoders 105a to 105e. The internal configurations of these encoders 105a to 105e are substantially the same as the corresponding encoders of FIG. 2, and the detailed configuration will be described later.

On the other hand, the output of the commonization analyzer 102 is also sent to the commonization data generator 104. There, the data to be shared by each channel is collected and recombined and output as one or a plurality of shared data.

The encoders 105a to 105e encode the outputs of the common data extractors 103a to 103e, respectively, and the encoders 105f to 105g output one or a plurality of common data output from the common data generator 104. Each encoded data is encoded.

These encoders 105a to 105g output the common parameter information used for the encoding together with the encoded data, and these are output by the multiplexer 10.
Sent to 6. The multiplexer 106 multiplexes the outputs of the encoders 105 a to 105 g into one bit stream and outputs the bit stream from the output terminal 107.

The bit stream from the output terminal 107 is recorded on a recording medium 109 such as an optical disc or a motion picture film by a recording device 108 which performs processing such as adding a predetermined error correction code and modulation. Or, although not shown,
It is transmitted by wire or wirelessly by a predetermined communication device.

Next, FIG. 3 shows the common analyzer 102.
The internal structure of is shown.

In FIG. 3, input terminals 121a to 121a
The audio data of each of the center (C), left (L), right (R), left surround (SL), and right surround (SR) channels supplied via 21e are shared processing analyzers 122a to 122a. 122i is selectively sent to 122i to analyze whether the use of each commonization method described later is effective and output the result. The common processing analyzers 122a to 122i correspond to the selection (combination) of common channels.

The common processing analyzers 122a to 122i described above.
The output results of all are sent to the common method selector 123. In this commonalization method selector 123, a method capable of commonalizing more channels, that is, in the commonalization processing analyzers 122a to 122i shown in FIG. Prioritizing the output of
The common method and the common range are determined, and the result is output.

Each common data extractor 124, based on the data related to the common obtained from the common technique selector 123, extracts only the data of the part to be common from the data of each channel of the input terminals 121a to 121e. The data are extracted and output from the corresponding output terminals 125a to 125e. It should be noted that the data regarding the commonization (common parameter information) from the common method selector 123 is used as a predetermined frame for each common data extractor 1 for each sound frame.
24a to 124e.

Here, in the case of five channels of the center (C), the left (L), the right (R), the left surround (SL), and the right surround (SR),
The types of common channel selection will be described with reference to FIG.

First, FIG. 4A shows that all channels are made common, and the commonization processing analyzer 122a for analyzing the effectiveness of the commonization method corresponds to this.

In FIG. 4B, the left side channel is center (C), left (L) and left surround (SL).
The channels are shared, and the right channel is center (C), light (R), or light surround (SR).
It is shown that channels are shared, and they correspond to the shared processing in the shared processing analyzer 122b or the shared processing analyzer 122c, respectively.

In FIG. 4C, the left (L) and left surround (SL) channels are commonly used as the left channel, and the right (R) and right surround (SR) channels are commonly used as the right channel. 9A and 9B respectively correspond to the commonization processing in the commonization processing analyzer 122d or the commonization processing analyzer 122e.

In FIG. 4D, three channels of center (C), left (L) and right (R) are shared as front channels, and left surround (S) as rear channels.
L) and light surround (SR) are shown to be shared by two channels, which correspond to the commonization processing in the commonization processing analyzer 122f or the commonization processing analyzer 122g, respectively.

FIG. 4E shows that the center (C) and left (L) channels are shared as the left front channel, and the center (C) and right (R) channels are shared as the right front channel. Common processing analyzer 1
22h or the common processing in the common processing analyzer 122i.

As described above, in the coding apparatus of this embodiment,
Not only does the common channel that uses the characteristics of the data be selected, but the common combination that uses the characteristics of the target playback environment is used, which makes it possible to reduce the discomfort that occurs due to the commonality. . Note that the combination of commonization disclosed in FIG. 4 is the best one that is considered to be effective, but within the scope not departing from the gist of the present invention,
Other combinations are possible.

Further, the respective commonalizing methods as shown in FIG. 4 can be changed between sound frames as a predetermined frame in a relationship as shown by an arrow in FIG. That is, A to E in FIG. 5 correspond to A to E in FIG.
It recognizes that the common method corresponding to E and connected by arrows changes between sound frames. For example, when a state where there is no common channel (NONE) is selected in a certain sound frame, the commonization method of C, D or E can be selected in the next sound frame. Therefore, if the D common method is selected, A, E, or NONE is selected in the next sound frame.
The common method of can be selected.

On the contrary, the absence of the arrow from NONE to A or B in FIG. 5 means that there is no common channel (NO.
From the sound frame in the (NE) state, the next sound frame indicates that sudden selection of A or B is prohibited. In this way, the sound image localization becomes good by giving a predetermined relationship to the selection of the commonalization method among the sound frames.

Further, as a common method, it is possible to make a plurality of common methods shown in FIG. 4 exist in the same sound frame.

For example, a method is conceivable in which the audio signal of each channel is analyzed for each specific frequency band, and the common method is selected for each specific frequency band. That is, a frequency converting means for converting a signal on the time axis into a signal component on the frequency axis is provided inside the common processing analyzer 122 or in the preceding stage of the input terminal 121, and the frequency axis obtained by this conversion is obtained. It is possible to use a method in which analysis is performed for each specific frequency band from the above signal and a commonalization method is selected based on the obtained analysis result. By this,
For example, in the high frequency range, all channels are shared (A in FIG. 4),
In the middle frequency range, it is possible to perform common processing by using two types of methods of commonizing the left channel and the right channel (C in FIG. 4). By doing so, it is possible to perform more effective commonization processing.

Further, in the same specific frequency band of the same sound frame, for example, the left (L) channel and the left surround (SL) channel are made common, and the right (R) channel and the right surround (SR) channel are made common. By using a method having a plurality of common channels, more effective common processing can be performed.

In addition, for example, regarding the center (C) channel, it is considered that there are two channels having twice the power, and this is divided, and the left (L) and left surround (SL) channels are shared, and It is also possible to improve the efficiency of the commonization by using the method of recording the signals of the divided channels for each of the commonalized (R) and write surround (SR) channels.

Furthermore, the applicant has previously filed international application number PCT / JP.
94/00880, International filing date: Uses the coding / decoding method proposed in the specification and drawings of May 31, 1994 to separate / encode a signal component into a noise component and a tone component. Then, for example, it is possible to perform processing such that all channels are made common for noise components (A in FIG. 4) and left and right channels are made common for tone components (C in FIG. 4).

Next, FIG. 6 shows the structure of a decoding apparatus to which the decoding method of the present invention is applied. The decoding apparatus according to the present embodiment is a decoding apparatus that realizes multi-channel decoding by using a plurality of single-channel compression code decoders (for example, decoders corresponding to the so-called ATRAC system described above).

That is, the decoding apparatus of this embodiment is similar to that shown in FIG.
As shown in FIG. 7, a part or all of the digital audio signals of a plurality of channels are treated as one or a plurality of commonized signals, and the commonization is performed according to the frequency characteristics of the digital audio signals and the intended reproduction environment. It is a decoding device for decoding encoded digital audio signals of a plurality of channels including signals whose channel combinations have been changed, by using common parameter information at the time of the encoding. This decoding device decodes the non-common signal and the common signal, distributes the decoded common signal to a plurality of channels according to the common parameter information, and Decoders 133f to 133g, a common data distributor 134, and a common data combiner 135a are provided as decoding means for recovering the digital audio signals of the plurality of channels by combining with the decoded non-common signals of the channels. ~
135e.

Further, in FIG. 7, for comparison with the decoding apparatus of the present embodiment, a multi-channel decoding apparatus which performs decoding for each channel (multi-channel decoding when the present invention is not used Shows the configuration of the device). In the example of FIG. 7, the same reference numerals are given to the portions corresponding to those in FIGS. 1 and 2, and the description thereof is omitted for easy understanding.

Prior to the description of FIG. 6, in the configuration of FIG. 7, the encoded bit stream data supplied through the input terminal 131 is the demultiplexer 132.
In, it is divided into encoded data of each channel and sent to the decoders 133a to 133e. Each decoder 133a-1
The audio data decoded in 33e as described later is output from the output terminals 136a to 136e.

On the other hand, the bit stream supplied through the input terminal 131 of the decoding apparatus according to the embodiment of the present invention shown in FIG. 6 is sent to the demultiplexer 132. Here, since data (common parameter information) indicating the common channel is included in the bit stream together with the coded data and common data of each channel, in the demultiplexer 132, , The encoded data and the common parameter information used for the encoding are divided for each channel, and the decoder 1
33a-133g.

Decoders 133f to 133g corresponding to the shared data channels output the decoded shared data and the shared parameter information, and send them to the shared data distributor 134. The common data distributor 134 creates data for each channel from one or a plurality of common data using the common parameter information and distributes the data to the corresponding channel.

Common data synthesizers 135a-135e
Outputs the outputs from the decoders 133a to 133e of the respective channels and the output from the common data distributor 134, and outputs the decoded data of the respective channels from the output terminals 136a to 136e.

As described above, in the decoding apparatus of this embodiment,
The common data distributor 134 is used to create data for each channel from one or a plurality of common data based on the common parameter information, and the common data combiner 135 is used.
Can be used to decode digital signals of a plurality of channels by synthesizing the data with unshared data of each channel. Even if there are multiple types of channels that consist of common data, and if there are multiple common processing methods, the data of a specific channel is further divided into multiple pieces to form multiple common data. Even in the case of being encoded into, the common data distributor 134 alone can perform the decoding by handling the distribution.

Next, the commonization of the multi-channel data does not deviate from the single-channel coding method used in the embodiment, and the commonization is performed with the data that is not standardized in the coded data state. FIG. 8 shows the configuration of the decoding device when it can be combined with the existing data.

In FIG. 8, the demultiplexer 13
2 divides the unshared data of each channel, the shared data, and the shared parameter information from the bit stream supplied via the input terminal 131, and the unshared data of each channel is The common data and the common parameter information sent to the common coded data synthesizers 138a to 138e share the common data distributor 13 with each other.
Sent to 7.

The common data distributor 137 creates data for each channel from one or a plurality of common data using the common parameter information and distributes the data to the corresponding channels.

The common data distributed from the common data distributor 137 to each channel and the non-common data of each channel output from the demultiplexer 132 correspond to common coded data. It is sent to the synthesizers 138a to 138e. The common encoded data synthesizers 138a to 138e synthesize the supplied data and output the encoded data as they are.

In each of the next decoders 133a to 133e,
Corresponding common coded data synthesizers 138a-1
Decode the output from 38e. Each of these 133a-1
The output of 33e is output from the corresponding output terminals 136a to 136e as data of each channel.

As described above, in the decoding apparatus of this embodiment,
Since the common data distributor 137 and the common coded data synthesizers 138a to 138e are provided before the processing of the decoder 133, the scale of the decoding device can be reduced.

Further, in the encoding method and apparatus of the present invention, the following method using the reproduction environment of the channel can be used as a method for enabling reproduction with less discomfort in hearing.

First, it is possible to use a method of changing the processing method to be treated as common data according to the reproduction environment recommended for audio data.

That is, when the five channels shown in FIG. 4A are shared, for example, the center (C), left (L), right (R), left surround (SL), right surround ( SR) for each channel signal, C: L: R: SL: SR = 1.0000: 0.7071: 0.7071:
Effective level sharing can be achieved by performing level conversion at a ratio of 0.5000: 0.5000 and then synthesizing and then reproducing from one channel at the time of reproduction or distributing to all channels at the same ratio.

Further, three channels of center (C), left (L) and left surround (SL) shown in FIG. 4B,
When the three channels of the center (C), the light (R), and the light surround (SR) are shared, for example, C: L: SL = 0.7071: 1.0000: 0.7071 C: R: SR = 0.7071: 1.0000: 0.7071. The use of such a ratio enables effective sharing.

When the left (C) and left surround (SL) 2 channels and the right (R) and right surround (SR) 2 channels shown in C of FIG. 4 are commonly used, for example, L: SL = 1.0000: 0.7071 R: SR = 1.0000: 0.7071 The ratio can be effectively shared.

When the left (L), center (C) and right (R) 3 channels and the left surround (SL) and right surround (SR) 2 channels shown in D of FIG. For example, if a ratio of C: L: R = 1.0000: 0.7071: 0.7071 SL: SR = 0.7071: 0.7071 is used, effective sharing becomes possible.

Left (L), center (C) 2 channels, right (R), center (C) shown in E of FIG.
When the two channels are shared, for example, effective rationalization becomes possible by using a ratio of C: L = 0.7071: 1.0000 C: R = 0.0771: 1.0000.

The above ratios are the best values at the present time obtained by the inventor of the present invention through hearing experiments and the like, and may take different values depending on future experiments.

In addition, in order to enable reproduction that does not cause a sense of discomfort to the ears by the encoding method and apparatus of the present embodiment described above, the data before the commonization is restored separately from the information of the commonization data. It is also possible to adopt an encoding method that includes information for

FIG. 9 and FIG. 10 show a configuration for realizing a method for extracting parameters for reproducing the data used for commonization of each channel from the commonized data. FIG. 9 shows a configuration corresponding to the common portion of FIG.
FIG. 10 shows a configuration in which a common parameter extractor 141 is added to FIG.

Further, FIGS. 11 and 12 show a configuration for realizing a method for adjusting using the parameter including the common data in the code. FIG. 11 is a configuration showing a part for distributing the common data of FIG. 6 to each channel,
FIG. 12 shows a configuration in which the common parameter adjuster 142 is added to FIG.

9 to 12, components corresponding to those in FIGS. 1 and 6 are designated by the same reference numerals, and detailed description thereof will not be given.

First, in FIG. 9, terminals 101 and 10
Data of corresponding channels are supplied to 1a to 101e, respectively. The data output from the commonization analyzer 102 and input to the commonization data extractor 103 and the commonization data generator 104 are the data used for commonization and its information, and the number of channels of the sound source data exists. To do. If the data of the corresponding channel is not used for commonization at all, the information that data is not used is sent. on the other hand,
The data output from the common data generator 104 and sent to the multiplexer 106 are the common data and its information, and there are the same number of common channels. How many common channels exist depends on the common method.

On the other hand, in FIG. 11, the data distributed for each corresponding channel by the common data distributor 134 is sent to the common data combiner 135 and combined with the data coded for each corresponding channel. Is
It is output as the decoded data of each channel.

Further, in the configuration of FIG. 9, as shown in FIG. 10, the common parameter extractor 14 is provided for each channel.
1 can be added. The common parameter extractor 141 inputs the data and its information used for commonization for each channel, and all the common data and its information. The common parameter extractor 141 uses this to analyze the degree of dependence of each common channel on the data of the channel and a method for restoring this common channel, and for example, for each frequency band unit used for encoding. Alternatively, the scale parameter of the channel in units of a plurality of bands or the scale parameter ratio between the frequency bands in the channel is obtained. This is multiplexer 1
Send to 06 to include in code.

Also in the decoding apparatus of FIG. 11, as shown in the decoding apparatus of FIG. 12, a common parameter adjuster 142 is added for each channel. The common parameter adjuster 142 receives the common data of the corresponding channel output from the common data distributor 134 and the information thereof, and the common parameter information of the corresponding channel output from the demultiplexer 132. By using this, in the common parameter adjuster 142, the common data is changed by utilizing a method for returning the dependence of the data of the common channel in each common channel and the commonization. As a result, a sound field closer to the original signal data of the channel can be reproduced as compared with the decoding device of FIG.

This system can be used as an independent system regardless of the reproduction environment of the channel. However, when the reproduction environment is specified, it is possible to predict the dependence of data, so that the data and the reproduction can be predicted. The more effective common parameter information can be created by analyzing the common parameters using the environment.

Further, in the encoding method and apparatus of the present embodiment, in order to enable reproduction without feeling uncomfortable to the auditory sense, a common channel is selected or a common processing method is selected between sound frames. There is an encoding method using the time change information of.

Here, the sound frame indicates a processing unit of audio data at the time of performing encoding and decoding,
The so-called ATRAC method used in this embodiment has 512 samples at a sampling frequency of 44.1 kHz.

By the way, the encoding method and apparatus of this embodiment can change the selection of the channel to be shared or the selection of the common processing method for each sound frame.
If you select the best channel and processing method to obtain playback that does not feel strange within each sound frame, the channel selection and processing method will change for each sound frame, and this switching will cause a sense of discomfort. There are cases.

Therefore, in the channel selection, the transition of the selection is monitored in each sound frame, and, for example, a method of preventing continuation of commonization of all channels and non-commonization of all channels,
By adopting a method of limiting the change of selection in the steady state where the change of the input data is small, it is possible to prevent the generation of a sense of discomfort due to switching.

In selecting the common processing method,
The difference in sound quality due to the difference in processing method is larger than that in channel selection, and since the encoding device and the decoding device need to be changed depending on the processing method, frequent switching in sound frame units is not suitable. It is appropriate to switch at a frequency of at least several sound frames.

Next, another embodiment of the present invention will be described.

The channel selection in the above-mentioned embodiment has been described in the case of 5 channels of center (C), left (L), right (R), left surround (SL) and right surround (SR). FIG. 13 shows channel selection in the case of 7 channels including the left center (CL) channel and the right center (CR) channel.

FIG. 13A shows that all channels are made common.

In FIG. 13B, four channels of a center (C), a left center (CL), a left (L), and a left surround (SL) are shared as a left channel, and a center (C) and a left center are used as a right channel. (CR), write (R), and write surround (SR) are shared.

In FIG. 13C, the left channel (left), left (L), left surround (S) are shown as left channels.
It is shown that the three channels L) are made common and the three channels of right channel (CR), write (R), and write surround (SR) are made common.

In FIG. 13D, five channels of center (C), left center (CL), left (L), right center (CR) and right (R) are shared as front channels, and left channels are used as rear channels. It shows that two channels of the center (SL) and the light center (SR) are shared.

In E of FIG. 13, three channels of the center (C), the left center (CL) and the left (L) are shared as the left front channel, and the center (C), the right center (CR) and the right ( It is shown that three channels of R) are made common.

In FIG. 13F, the left center (CL) and left (L) channels are commonly used as the left front channel, and the right center (CR) and right (R) channels are commonly used as the right front channel. Is shown.

Also in the case of the other embodiments, it is appropriate to carry out a method in which a larger number of channels can be made common, that is, by performing priority processing in which A of FIG. 13 is the highest and F of FIG. 13 is the lowest. Common channel selection is possible.

By using the combination of the above commonalization,
Even in the case of 7 channels, it is possible to reduce the discomfort caused by the commonization.

Further, in FIG. 13, it is conceivable that a subwoofer (SW) channel is further added to form 8 channels, but this subwoofer (SW) channel is a channel for reproducing low frequency. Therefore, it is not suitable for standardization. Therefore, it is possible to easily add to the encoding and decoding device without adding to the common processing.

Next, the specific structure and operation of the encoder 105 will be described with reference to FIGS. In addition,
FIG. 14 shows the configuration of the encoder 105 for one channel.

In FIG. 14, at the input terminal 24, the audio data of the remaining part (sampled and quantized) from which the part to be made common is extracted from the original audio data by the common data extractor 103. Audio signal) is supplied. The signal supplied to the input terminal 24 is first converted by the band division filter 401 from 0 to
Low frequency of 5.5 kHz, 5.5 kHz to 11 kHz mid range, and 11 kHz or more (11 kHz to 22 kHz) 3
It is divided into signal components on the time axis of one frequency band.

Of the signal components in these three frequency bands, the low frequency signal component from the band division filter 401 is the MDCT (Modified Discrete Cosine Transfor).
m: MDCT circuit 40 for performing improved discrete cosine transform) operation
In 2L, the signal component in the middle range is also MCT which performs MDCT calculation
In the DCT circuit 402M, the high frequency signal component is MDC
Sent to the T circuit 402H and these MDCT circuits 402L
At ~ 402H, each is decomposed into signal components on the frequency. At this time, the time block length when performing the MDCT can be variable for each frequency band,
Control the effective transmission and quantization noise of the signal component by shortening the time block length to increase the time resolution in the portion where the signal component changes rapidly and increasing the time block length in the portion where the signal component is stationary. To do.

The time block length is determined by the block size evaluator 403. That is, the signal components of the three frequency bands from the band division filter 401 are also sent to the block size evaluator 403, the block size evaluator 403 determines the time block length in the MDCT, and the determined time is determined. Information indicating the block length is sent to the MDCT circuits 402L to 402H.

Of the two types of time block lengths when the time block length in MDCT is varied, the long time block length is called a long mode and corresponds to a time of 11.6 ms. Also, the short time block length is called short mode, and 1.45 m in the high range (11 kHz or more).
Up to s, low range (less than 5.5 kHz) and middle range (5.5 kHz)
(Hz to 11 kHz), the time resolution is increased up to 2.9 ms.

In this way, the two-dimensional area of time and frequency (this is a block floating unit: Block Fl
The audio signal decomposed into the above signal components is divided into a total of 52 block floating units in the low band, middle band, and high band by the normalization circuits 404L to 404H and standardized for each unit. (Normalized) (scale factor is determined).

Further, the bit allocator 405 analyzes what kind of component the audio signal is composed by utilizing the characteristics of human hearing. The result of this analysis is sent to the requantizer 406 to which the signals for each unit from the normalization circuits 404L to 404H are supplied.

The re-quantizer 406 determines, based on the analysis result, with what degree of accuracy each unit is quantized and parameterizes it (determines the word length), and at the same time determines the obtained quantum. Requantization is performed with the accuracy of quantization.

Finally, the formatter 407 converts each parameter information for each unit and the requantized signal component on the frequency axis into a bit stream in one channel to be sent to the multiplexer 106 of FIG. 1 according to a predetermined format. Assemble. The output of the formatter 407 is output from the output terminal 25 as a bit stream.

Although the bit stream is not shown,
The data is recorded on a recording medium such as an optical disc or a movie film by a recording device that performs predetermined error correction, modulation, and other processing.

Here, the encoding operation as described above is as follows.
It is performed in units of sound frames.

Further, the bit allocator 405 has a concrete structure as shown in FIG.

In FIG. 15, the input terminal 521 is supplied with signal components on the frequency axis (hereinafter referred to as frequency domain data) from the MDCT circuits 402L, 402M and 402H.

This frequency domain data is sent to the energy calculation circuit 522 for each band, and the energy of each critical band (critical band) is calculated, for example, as the sum of the squared amplitude values in the band. It is required by things. Instead of the energy for each band, a peak value, an average value, etc. of the amplitude value may be used. As an output from the energy calculation circuit 522, for example, the sum total value of each band is generally called a Bark spectrum. FIG. 16 shows the Bark spectrum SB for each such critical band. However, in FIG. 16, the number of bands of the critical band is represented by 12 bands (B1 to B12) in order to simplify the illustration.

Here, in order to consider the effect of so-called masking of the Bark spectrum SB, a convolution process is performed in which the value of the Bark spectrum SB is multiplied by a predetermined weighting function and added. . Therefore, the output of the energy calculation circuit 522 for each band, that is, each value of the Bark spectrum SB is sent to the convolution filter circuit 523. The convolution filter circuit 523 is, for example, a plurality of delay elements that sequentially delay input data, and a plurality of multipliers that multiply outputs from these delay elements by a filter coefficient (weighting function) (for example, 25 corresponding to each band). Number of multipliers), and a sum adder that sums the outputs of the multipliers.

The masking is a phenomenon in which one signal is masked by another signal and becomes inaudible due to human auditory characteristics. This masking effect includes a time-axis masking effect by an audio signal in the time domain and a same-time masking effect by a signal in the frequency domain. Due to these masking effects, even if there is noise in the masked portion, this noise cannot be heard. Therefore, in the actual audio signal, the noise within the masked range is regarded as an acceptable noise.

Here, a specific example of the multiplication coefficient (filter coefficient) of each multiplier of the convolution filter circuit 523 will be described. When the coefficient of the multiplier M corresponding to an arbitrary band is 1, the multiplier M-1 gives a coefficient of 0.15, multiplier M-2 gives a coefficient of 0.0019, and multiplier M-3 gives a coefficient of 0.0000.
086, multiplier M + 1 gives a coefficient of 0.4, multiplier M + 2
By multiplying the output of each delay element by a coefficient of 0.06 and a coefficient of 0.007 by a multiplier M + 3, the value of the Bark spectrum SB is convoluted. However, M is an arbitrary integer of 1 to 25.

Next, the output of the convolution filter circuit 523 is sent to the subtractor 524. The subtractor 524 calculates a level α corresponding to an allowable noise level described later in the convoluted area. The level α corresponding to the permissible noise level (permissible noise level) is a level at which the critical noise band becomes the permissible noise level for each band by performing inverse convolution processing, as described later. is there. here,
The subtractor 524 is supplied with an allowance function (function expressing a masking level) for obtaining the level α. The level α is controlled by increasing or decreasing this allowance function. The permissible function is supplied from the (n-ai) function generating circuit 525 as described below.

That is, the level α corresponding to the allowable noise level can be obtained by the following equation, where i is the number given in order from the low band of the critical band.

Α = S- (n-ai) In this equation, n and a are constants and a> 0, S is the intensity of the convolution-processed Bark spectrum, and (n-ai) is an allowable function. Becomes

As an example, n = 38 and a = -0.5 can be used.

In this way, the level α is obtained, and this data is transmitted to the divider 526. The divider 526 is for deconvolution of the level α in the convolved area. Therefore, by performing the inverse convolution processing, the masking threshold can be obtained from the level α. That is, this masking threshold becomes the allowable noise level. Although the above-mentioned inverse convolution processing requires complicated calculation, in this embodiment, the inverse convolution is performed using the simplified divider 526.

Next, the masking threshold signal is transmitted to the subtractor 528 via the synthesizing circuit 527. Here, the output from the energy detection circuit 522 for each band, that is, the signal of the above-described Bark spectrum SB is supplied to the subtractor 528 via the delay circuit 529. Therefore, the subtractor 528 performs a subtraction operation on the masking threshold signal and the signal of the bark spectrum SB, so that the value of the bark spectrum SB becomes the masking threshold value as shown in FIG. The level below the level indicated by the MS will be masked. The delay circuit 529 is provided for delaying the signal of the Bark spectrum SB from the energy detection circuit 522 in consideration of the delay amount in each circuit before the synthesis circuit 527.

The output from the subtracter 528 is taken out via the allowable noise correction circuit 530 and the output terminal 531. For example, the ROM in which the distribution bit number information is stored in advance.
Etc. (not shown). The ROM or the like is distributed for each band according to the output (the level of the difference between the energy of each band and the output of the noise level setting means) obtained from the subtraction circuit 528 through the allowable noise correction circuit 530. Outputs bit number information.

The distribution bit number information thus obtained is sent to the requantizer 406 of FIG. 14, so that the MDCT circuits 404L and 4040 in the requantizer 406.
Each data in the frequency domain from 4M and 404H is requantized by the number of bits assigned to each band.

That is, in summary, in the requantizer 406, the energy or peak value of the band obtained by further dividing the critical band into a plurality of bands in each band band (critical band) of the critical band or in the high band and the noise. The data for each band is quantized by the number of bits distributed according to the level of the difference from the output of the level setting means.

By the way, at the time of synthesizing by the above-mentioned synthesizing circuit 527, the data showing the so-called minimum audible curve RC which is the human auditory characteristic as shown in FIG. The masking threshold MS can be combined. In this minimum audible curve, if the absolute noise level is below this minimum audible curve, the noise will not be heard.

Even if the coding is the same, the minimum audible curve is different, for example, due to the difference in reproduction volume during reproduction. However, in a realistic digital system, there is not much difference in the characteristics of the music signal into the 16-bit dynamic range, so that, for example, if the quantization noise in the most audible frequency band around 4 kHz is not heard, In other frequency bands, it is less problematic to consider that the quantization noise below the level of this minimum audible curve cannot be heard.

Therefore, for example, assuming that the system is used so that noise around the dynamic range of 4 kHz is not heard, the minimum audible curve RC and the masking threshold MS signal are combined together to obtain an allowable noise level. In this case, the allowable noise level in this case can be considered up to the shaded portion in FIG. In this embodiment, the level of 4 kHz of the minimum audible curve is set to the minimum level equivalent to 20 bits, for example. Further, FIG. 17 also shows the signal spectrum SS at the same time.

In the allowable noise correction circuit 530,
The allowable noise level in the output from the subtractor 528 is corrected based on the information of the equal loudness curve sent from the correction information output circuit 533, for example. Here, the equal loudness curve is a characteristic curve relating to human auditory characteristics, for example, a curve obtained by obtaining the sound pressure of sound at each frequency that sounds the same as a pure tone of 1 kHz, and connecting the curves. Also called sensitivity curve. Further, this equal loudness curve is the minimum audible curve R shown in FIG.
It draws a curve substantially the same as C.

In this equal loudness curve, for example, in the vicinity of 4 kHz, the sound pressure becomes 8 to 10 at 1 kHz.
Even if it goes down by dB, it sounds as loud as 1 kHz. vice versa,
In the vicinity of 50 Hz, the sound level is not heard unless it is higher than the sound pressure at 1 kHz by about 15 dB. Therefore, noise exceeding the level of the above minimum audible curve (allowable noise level)
It is understood that it is better to have a frequency characteristic given by a curve corresponding to the equal loudness curve. From this, it can be seen that correcting the permissible noise level in consideration of the equal loudness curve is suitable for human hearing characteristics.

Next, FIG. 18 shows the encoder 10 of FIG.
5 shows a specific configuration of the decoder 133 of FIG.

That is, the decoder shown in FIG. 18 is a code for one channel of each channel read from a recording medium such as an optical disc or a movie film described later by a reproducing unit such as a magnetic head or an optical head. The decoded signal is decoded.

In FIG. 18, coded data from the demultiplexer 132 of FIG. 5 is supplied to the terminal 26, and this is sent to the deformatter 411. The deformatter 411 performs the reverse processing corresponding to the formatter 407 to obtain each parameter information for each unit and the requantized signal component on the frequency axis (that is, the quantized MDCT coefficient). .

The quantized MDCT coefficient for each unit from the deformatter 411 is sent to the low frequency decoding circuit 412L, the middle frequency decoding circuit 412M and the high frequency decoding circuit 412. In addition, these decoding circuits 41
Parameter information is also given to the 2L to 412H from the deformatter 411. Each decoding circuit 412L to 412H
Then, the bit allocation is canceled using the parameter information and the decoding is performed.

The outputs of these decoding circuits 412L-412H are sent to the corresponding IMDCT (inverse MDCT) circuits 413L-413H. The parameter information is also sent to each of the IMDCT circuits 413L to 413H, and here, the signal component on the frequency axis is converted into the signal component on the time axis. The band-combining circuit 414 decodes the signal components of these partial bands on the time axis into full-band signals.

Next, an example in which the data encoded by the encoding method or apparatus of this embodiment is recorded on a motion picture film as an example of the recording medium will be described with reference to FIG.

That is, the encoded data is recorded on the motion picture film 1 shown in FIG. The recording position of the encoded data on the motion picture film 1 is, for example, as shown in FIG.
Recording area 4 between the perforations 3 of the motion picture film 1 as shown in FIG. 19A, or the recording area 4 between the perforations 3 on the same side on both sides of the motion picture film 1 as shown in FIG. The longitudinal recording area 5 between the perforation 3 of the motion picture film 1 and the edge of the motion picture film 1 as shown in FIG. 19C, and the perforation 3 of the motion picture film 1 as shown in FIG. 19D. The longitudinal recording area 5 between the edge and the edge of the motion picture film 1 and the recording area 4 between the perforations 3 can be cited as examples.

Finally, an example in which data encoded by the encoding method and apparatus of this embodiment is recorded on an optical disk as an example of a recording medium will be described with reference to FIG.

FIG. 20 shows a part of a coded bit stream, and particularly shows an example of header data of each channel used when the present invention is implemented.

The header data consists of several flags, and 1/0 of these flags describes many conditions regarding the bit stream that follows.
Here, only a part of the bitstream is disclosed, and the description of the conditions not directly related to the present invention will be omitted.

The channel common mode uses the cplchf flag. [Su] is the sound frame number, [ch]
Indicates the channel number. The cplchf flag is a 4-bit code and up to 4 can be defined. If there is no 1 in any bit, that is, 0000 (bit indication) is defined, it is determined that there is no common data in the bit stream of this channel.

When the mode of sharing all channels is selected, the cplchf flags of all channels are set to 1000.
Therefore, the common data of all channels is stored in the first acbs (common data).

On the other hand, when the mode for sharing the left channel / the mode for sharing the right channel is selected, the c of the channels selected for sharing the left channel is selected.
The plchf flag is set to 1000, the cplchf flag of the channel selected for commonization of the right channel is set to 0100, and 1
The common data of the left channel is stored in the second acbs, and the common data of the right channel is stored in the second acbs.

That is, it is possible to select which acbs to use for each channel by the bit of the cplchf flag.

It is possible to change the combination by using such an encoded bit stream and header data.

FIG. 21 schematically shows the structure of the coded bit stream. Reference numeral 150 indicates a header of the entire bitstream, and reference numerals 151 to 151
Reference numeral 15 denotes the data area of each channel in 155.
Reference numerals 6 to 159 denote common data areas for four channels.

Data areas 151 to 155 of each channel
Are common flag (cpl use flag) 160, common parameter (cpl parameter) 161, and data (real dat).
a) Including 162. Also, common flag (cpl use flag) 1
20, 60 is composed of 4 bits (cpl1-4 use bits) 170 to 173, as described as cplchf in FIG.

Next, FIG. 22 shows the common analyzer 10.
2 shows another embodiment.

In FIG. 22, the center (C), the left (L), which are supplied through the input terminal 101,
The audio data of each channel of right (R), left surround (SL), and right surround (SR) is sent to the orthogonal converters 201a to 201e, where it is converted into signal components on the frequency axis and output. .

The frequency characteristic evaluators 202a to 202e are
Based on the data of the signal components on the frequency axis of each channel obtained from the orthogonal transformers 201a to 201e, parameters of human auditory characteristics such as so-called minimum audible curve and masking threshold are obtained, and the parameters on the frequency axis are obtained. The result is output together with the signal component.

In the common processing selector 203, the encoding target bit rate and the frequency characteristic evaluators 202a to 202 are used.
Based on the data regarding the commonization obtained from the evaluation in e, the frequency band is selected such that the absolute level of the quantization noise generated by the commonization is equal to or less than the minimum audible curve. As a result, the quantization noise generated by the commonization cannot be heard. The selection result is output terminal 204.
Output from the common data extractors 103a to 103e
And the common data generator 104. It should be noted that the data regarding commonization (common parameter information) output from the output terminal 124 is output in a predetermined frame unit (for example, a sound frame).

As described above, in the coding apparatus of this embodiment,
By selecting the common frequency using the characteristics of the data, it is possible to reduce the discomfort caused by the common frequency.

Further, the method of commonization performed by the commonization processing selector 203 can be changed between sound frames as a predetermined frame. This makes it possible to suppress the change in the sound field due to the commonization by selecting the most suitable common frequency band between the sound frames.

Further, in FIG. 22, it is possible to make a plurality of selections of commonization processing within the same sound frame. For example, when the frequency band below the minimum audible curve is expanded by independently encoding one or a plurality of channels in a specific frequency band without commonization,
By performing the commonization process by changing the combination of channels to be shared in a plurality of frequency bands, more effective commonization becomes possible.

Alternatively, it is possible to allow a plurality of common combinations to exist simultaneously in a specific frequency band. For example, in the case of data in which it is effective to share the front side channel and the rear side (surround) channel separately, by creating a plurality of common channels with the same or different frequency bands to be shared, the data characteristics can be improved. It is possible to achieve effective standardization.

The above-described coding method and decoding method of the present invention can be applied not only to the so-called ATRAC method used in the embodiments but also to any coding method. In particular, the effect is high in a coding method in which frequency information is converted by orthogonal conversion.

[0163]

In the encoding method and apparatus of the present invention, the compression rate is increased by treating the digital signals of at least some channels of the digital signals of a plurality of channels as common signals and performing the encoding process. For example, by changing the combination of channels to be shared according to the target playback environment of the audio signal, or by changing the processing method to handle as a common signal according to the recommended playback environment of the audio signal, the sound field due to the commonization Can be suppressed.

Further, in the encoding method and apparatus of the present invention, a predetermined time frame (eg sound frame)
It is possible to avoid an unstable reproduced sound field due to a sudden change in the combination of channels shared between the channels and the processing method handled as common data.

Furthermore, in the decoding apparatus of the present invention,
By decoding the digital signals of a plurality of channels from at least one common signal and changing the processing method for handling the common signal according to the reproduction environment recommended by the coded signal, It is possible to suppress the change.

Further, the recording medium of the present invention records the signal encoded by the encoding method and apparatus of the present invention, and provides a more stable reproduced sound field by using a movie film. Is possible.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a schematic configuration of a multi-channel audio encoding device of an embodiment which is an encoding device of the present invention.

FIG. 2 is a block circuit diagram showing a configuration of a multi-channel audio encoding device when the present invention is not used.

FIG. 3 is a block circuit diagram showing the configuration of a common analyzer of the encoding device according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating types of common channel selection according to an embodiment of the present invention.

FIG. 5 is a diagram for explaining a change between surround frames of a common channel.

FIG. 6 is a block circuit diagram showing a schematic configuration of a multi-channel audio decoding device which is a decoding device according to an embodiment of the present invention.

FIG. 7 is a block circuit diagram showing a configuration of a multi-channel audio decoding device when the present invention is not used.

FIG. 8 is a block circuit diagram showing a modified example of the multi-channel audio decoding device according to the embodiment of the present invention.

FIG. 9 is a block circuit diagram showing a configuration example for realizing a common parameter encoding method according to an embodiment of the present invention.

FIG. 10 is a block circuit diagram showing another configuration example for realizing the common parameter encoding method according to the exemplary embodiment of the present invention.

FIG. 11 is a block circuit diagram showing a configuration example for realizing the decoding method of the common parameter according to the exemplary embodiment of the present invention.

FIG. 12 is a block circuit diagram showing another configuration example for realizing the decoding method of the common parameter according to the exemplary embodiment of the present invention.

FIG. 13 is a diagram illustrating types of common channel selection in the case of seven channels according to the embodiment of this invention.

FIG. 14 is a block circuit diagram showing a specific configuration of the encoder of the encoding device according to the embodiment.

FIG. 15 is a block circuit diagram showing a specific configuration of the bit distributor of the encoder.

FIG. 16 is a diagram for explaining a Bark spectrum and a masking threshold level.

FIG. 17 is a diagram showing a composite of a signal level, a minimum audible curve, and a masking threshold.

FIG. 18 is a block circuit diagram showing a specific configuration of the decoder of the decoding device in the example.

FIG. 19 is a diagram for explaining a position where an encoded signal is recorded on a motion picture film.

[Fig. 20] Fig. 20 is a diagram illustrating an example of header data of each channel of an encoded bitstream.

FIG. 21 is a diagram schematically showing the configuration of an encoded bitstream.

FIG. 22 is a block circuit diagram showing the configuration of a common analyzer of an encoding device according to another embodiment of the present invention.

[Explanation of symbols]

102 Common analyzer 103 Common data extractor 104 Common data generator 105 encoder 106 multiplexer 122 Common Processing Analyzer 123 Common method selector 124 Common data extractor 132 demultiplexer 133 decoder 134, 137 Common data distributor 135 Common data synthesizer 138 Common coded data synthesizer 141 Common Parameter Extractor 142 Common Parameter Adjuster

─────────────────────────────────────────────────── --- Continuation of the front page (56) Reference JP-A-6-149292 (JP, A) JP-A-63-182700 (JP, A) JP-A-7-283738 (JP, A) JP-A-7- 123008 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H03M 7/30 C10L 19/00 G11B 20/10 341

Claims (21)

(57) [Claims] 1. A coding method for coding a digital signal of a plurality of channels and outputting the coded digital signal and parameter information of the coding, wherein at least a part of channels of the digital signal of the plurality of channels is encoded. A common step of making a digital signal a common signal; a changing step of changing the combination of the common channels according to the frequency characteristics of the digital signal or a target reproduction environment; A parameter information output step of outputting parameter information indicating a combination, an encoding step of encoding and outputting the common signal, and a multiplexing step of multiplexing the parameter information and the encoded output. Characteristic encoding method. 2. The encoding step for encoding the commonized signal includes a variable step for adaptively varying the processing to be performed according to the content of the digital signal or a recommended reproduction environment. The encoding method according to claim 1. 3. The encoding method according to claim 2, wherein the variable step of adaptively varying the processing to be performed performs variable control in units of a predetermined time frame. 4. The encoding method according to claim 1, wherein in the changing step of changing the combination of channels to be made common, change control is performed in units of a predetermined time frame. 5. The encoding method according to claim 4, wherein a plurality of combinations of the channels to be shared are used within the same time frame. 6. The common signal is a signal in which a digital signal of any channel is divided and arranged between at least two channels.
The described encoding method. 7. For at least one of the digital signals of the respective channels to be made common, information for reproducing the signal before being made common is obtained for the digital signals of the respective channels, and the information is made a common signal. The encoding method according to claim 1, wherein the encoding method is included. 8. An encoding device for encoding digital signals of a plurality of channels and outputting parameter information of the encoding together with the encoded digital signals, wherein at least a part of the digital signals of the plurality of channels are digital signals. Is used as a common signal, changing means for changing the combination of channels to be made common according to the frequency characteristics of the digital signal and the intended reproduction environment, and the combination of the common channels. It has a parameter information output means for outputting the parameter information shown, an encoding means for encoding the common signal, and a multiplexing means for multiplexing the parameter information and the encoded output. Encoding device. 9. The encoding apparatus according to claim 8, wherein the encoding means changes the processing to be performed on the signals to be shared according to the content of the digital signal and the recommended reproduction environment. 10. The encoding apparatus according to claim 8, wherein the encoding means controls a change of the combination of the channels to be shared between predetermined time frames. 11. The encoding apparatus according to claim 8, wherein the encoding means controls a change of processing to be applied to the signals to be shared between predetermined time frames. 12. The encoding apparatus according to claim 8, wherein the encoding means divides a digital signal of an arbitrary channel into a plurality of common channels and arranges the divided signals. 13. The encoding apparatus according to claim 10, wherein the encoding means uses a plurality of types of the combination of channels to be made common within the same predetermined time frame. 14. The encoding means analyzes information for reproducing a signal before being made common with respect to a part or all of digital signals of the respective channels to be made common, and converts the information into a signal which is made common. The encoding device according to claim 8, wherein the encoding device is included. 15. A part or all of digital signals of a plurality of channels are treated as one or a plurality of common signals, and the common channels are processed according to frequency characteristics of the digital signals and a target reproduction environment. A decoding device for decoding encoded digital signals of a plurality of channels including a signal whose combination has been changed, using the parameter information of the encoding, wherein the decoding device decodes the commonized signal. Means, and a distribution means for distributing the decoded common signal to a plurality of channels according to the combination of the commonization, and restoring each digital signal of the plurality of channels based on the distributed commonized signal. And a restoring means for performing the decoding. 16. The decoding according to claim 15, wherein said decoding means changes the processing applied to said common signal in accordance with the recommended reproduction environment of said encoded digital signal. Device. 17. The decoding means decodes a plurality of coded signals used in a predetermined time frame in which the types of combinations of the common channels are the same. 15. The decoding device according to item 15. 18. The decoding means decodes a coded signal of an arbitrary channel, which is divided into a plurality of common signals and arranged and coded. Decoding device as described. 19. The decoding device adjusts the signal of each channel by using information for reproducing the signal before the commonization included in the commonized signal. Decryption device. 20. A combination of channels for handling at least one channel of digital signals of a plurality of channels as a common signal, and for performing the commonization according to a frequency characteristic of the digital signal and a target reproduction environment. A signal obtained by coding the changed common signal, parameter information indicating a combination of channels to be common, and a signal obtained by coding another signal excluding the common signal are used as coding parameters. A recording medium characterized by being recorded together with information. 21. The recording medium according to claim 20, wherein the recording medium is an optical disc or a movie film.